Hi

My data has the following setup. I have individual level data for years 1995, 2000, 2005, 2010 and 2015. The treatment happened at state level in different years between 2002 and 2014( For example state 1 in 2003, state 2 in 2011 etc). Some states did not get treated at all. I want to run a Staggered DID and compare differences in outcomes of treated versus non treated states.

Can I run the following regression for the same?

Yist = α + βTst + ϒs + θt + εist,
i – individual, s – state, t – year
Tst – Whether state s had the treatment by year t


1) Also, will it matter if I run the regression at individual or state level (since all the variation in the RHS is coming at the state level)
2) Since the treatment is given at the state level, the standard errors should be clustered at the state level , right?


Also, in this setup, how do I check for the parallel trends assumption?


Thanks.